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WinTR-20 Course February 20151 Muskingum-Cunge Flood Routing Procedure in NRCS Hydrologic Models Prepared by William Merkel USDA-NRCS National Water Quality and Quantity Technology Development Team Beltsville, Maryland

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WinTR-20 Course February 20152 NRCS Hydrologic Models WinTR-20 Computer Program for Project Formulation - Hydrology WinTR-55 Urban Hydrology for Small Watersheds Both programs are developed for Windows and are currently available in final release versions.

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WinTR-20 Course February 20158 Muskingum-Cunge Method Derived from convection-diffusion equation (simplification of full dynamic equations) K and X determined from hydraulic properties of the reach K is a timing parameter, seconds X is a diffusion parameter, no dimensions

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WinTR-20 Course February 201513 Assumptions / Limitations Equations developed for wide rectangular cross sections –width is top width –celerity is 5/3 velocity using Manning equation –Q is a reference discharge What width, celerity, and Q should be used for flood plain cross sections ?

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WinTR-20 Course February 201531 Application Strategy Select one cross section to represent the WinTR-20 reach. The velocity is the key factor to look at. Picking a cross section with an average velocity will give reasonable results. A computer program is being developed to derive an average rating from a group of HEC-RAS cross sections.